Not specifically Hekaton, introduced in SQL Server 2014 was the ability for you to perform asynchronous commits; ordinarily when you do a commit transaction the statement will not complete until the data is physically hardened off onto the storage media, Delayed Durability is a way to remove that latency headache.

In order to understand how in-memory tables function with regard to indexing, performance and the multi-version concurrency control (MVCC) used to do updates, inserts and deletes then you need a good understanding of Row Chains – this article covers the basics of Row Chains and also goes into more detail of how the Hash Index utilises them.

The new Range Index on an in-memory table uses a Bw-Tree structure which is an improvement over the standard B-Tree we are used to do as it offers latch and lock free modifications to greatly improve scalability across multiple cores and concurrent connections.